This invention relates to an optical motion detector of the type commonly referred to as a "mouse" because the body, which fits easily in the palm of the hand, is intended to be moved on a desk top with a cable connecting it to a computer resembling the tail of a mouse. The detected motion of the mouse is used as an input to the computer for such purposes as positioning a cursor on an image or text displayed on a cathode ray tube, or as an input to graphics being generated at the computer console.
The mouse is quickly becoming popular. Older mechanical mouse designs are being replaced by new designs that use optics instead of moving parts to detect motion. These optical mice improve the reliability and decrease the intermittent action so common with mechanical mice.
To date, all the optical mouse designs must be moved over a special surface pattern in order to sense their motion properly. One commercially available optical mouse uses a metal plate as a working surface on the desk top with orthogonal grid lines. Lines in one direction reflect infrared and lines in the other direction reflect visible light. Sensors within the mouse that are sensitive to only one color of light can thus detect motion in two directions independently. R. F. Lyon of Xerox Corporation developed an innovative optical mouse that integrated sensors onto the same chip with the processing of optical signals for detection of motion. However, his design requires a working surface consisting of a hexagonal grid of dark dots on a light background. An object of this invention is to relax the requirements on the working surface of the optical mouse. The object is to make an optical motion detector general enough to allow it to work on a wide variety of surfaces like those commonly found on desk tops, thus eliminating the need for a special working surface.